In 1982, Chevrolet grew tired of losing sales to the likes of the Nissan pickup and the Toyota truck, and decided to end its nine-year-long relationship with Isuzu, the maker of the Chevy LUV the automakers original compact truck and release its Chevy-built S10. With its heavy advertising, the S10 hit the ground running and continued unscathed until its replacement, the Colorado, entered the lineup in 2004. Finding the engine coolant temperature sensor in the 1994 model year S10 is a straightforward task most owners can perform. Testing and replacing the ECT sensor is slightly trickier.
Instructions
Locating the Engine Coolant Temperature Sensor
- 1
Trace the upper radiator hose toward the engine until you reach the metal housing connecting the hose to the engine; this is the thermostat housing.
2Look just below the thermostat housing to find the water inlet housing the metal component to which the thermostat housing bolts.
3Find the engine-coolant temperature sensor screwed into the passengers side of the water inlet housing.
Testing the Coolant Temperature Sensor
- 4
Allow the engine to cool until it is cool to the touch. Slowly unscrew the radiator cap to relieve pressure in the cooling system. This loss of pressure drops the coolant level below the ECT sensor.
5Pry upward on the locking tab on the ECT sensors wiring harness using a flat-head screwdriver, then unplug the wiring harness. Remove the ECT sensor using a ratchet and deep-well socket.
6Fill a pan with tap water and take the temperature of this water using a digital thermometer. Set a multimeter to read ohms and touch the multimeter probes to the two pins inside the ECT sensors receptacle. Read the ohms of resistance and compare it to the number displayed to the specifications below, using the water temperature as your guide. If the ECT sensor is not within these specifications, replace it. If it is within specification, continue to the next step.
At -40 degrees Fahrenheit, the multimeter should read roughly 100,700 ohms; roughly 25,000 ohms at 0 degrees Fahrenheit; roughly 12,300 ohms at 23 degrees Fahrenheit; roughly 3,520 ohms at 68 degrees Fahrenheit; roughly 1,800 ohms at 100 degrees Fahrenheit; roughly 467 ohms at 158 degrees Fahrenheit; and roughly 177 ohms at 212 degrees Fahrenheit.
7Place the pan of water on the stove and turn the stove on to heat the water to the next testing temperature from the unheated water in the above step, as listed. Periodically use the thermometer to check the water's temperature until it reaches the desired temperature, then remove the pan from the stove.
8Connect alligator clip connectors to the multimeter probes. Clip the alligator clips to the two pins inside the ECT sensors receptacle. Dip the ECT sensor into the heated water using needle-nose pliers, and compare the ohms displayed on the multimeter to the specifications listed. If the sensor passes this test, proceed to the next step. If the ECT sensor fails this test, replace it.
9Heat the water in the pan to the next testing temperature.
10Repeat steps 5 and 6 until you complete the 212-degrees Fahrenheit testing mark. If the sensor passed all tests, the fault is not in the ECT sensor. The likely failure is in the ECT sensors wiring or the vehicle control module.
Replacing the Engine Coolant Temperature Sensor
- 11
Unplug the ECT sensors wiring harness.
12Hand-thread a new ECT sensor into the water inlet housing and tighten it until snug with a ratchet and deep-well socket. Do not over-tighten the ECT sensor, as it breaks under relatively low torque. Plug the wiring harness into the receptacle on the ECT sensor.
13Start the engine and allow it to idle until it reaches operating temperature, roughly halfway up the temperature gauge. Watch the movement of the temperature gauge as the truck warms up to assure the sensor sends a signal to the VCM. If the gauge moves smoothly, you have repaired your sensor problems. If the gauge does not move at all or moves erratically, there are additional problems in the circuit.
